U.S. patent number 5,545,956 [Application Number 08/391,738] was granted by the patent office on 1996-08-13 for window wiper system for small windows.
This patent grant is currently assigned to Hughes Aircraft Company. Invention is credited to David M. Masarik, Paul R. Salvio, Kevin J. Wasserstein.
United States Patent |
5,545,956 |
Salvio , et al. |
August 13, 1996 |
Window wiper system for small windows
Abstract
A motor drive system for imparting oscillating motion to a
window wiper is disclosed which slows the wiper as it approaches
respective right and left positions and holds the wiper at the
right and left positions for a selectable delay interval in order
to avoid deleterious effects of instantaneous motor direction
reversal. The system includes a motor drive chip for generating the
drive signal to the window wiper motor, a programmable logic array
for sequencing the operation of the motor drive chip, and a delay
chip for timing the selected delay.
Inventors: |
Salvio; Paul R. (Palos Verdes
Estates, CA), Masarik; David M. (Laguna Beach, CA),
Wasserstein; Kevin J. (Manhattan Beach, CA) |
Assignee: |
Hughes Aircraft Company (Los
Angeles, CA)
|
Family
ID: |
46249560 |
Appl.
No.: |
08/391,738 |
Filed: |
February 21, 1995 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
263272 |
Jun 21, 1994 |
5479077 |
Dec 26, 1995 |
|
|
Current U.S.
Class: |
318/283; 318/443;
318/484; 15/250.31; 318/DIG.2 |
Current CPC
Class: |
B60S
1/3475 (20130101); B60S 1/08 (20130101); B60S
1/34 (20130101); B60S 1/3479 (20130101); B60S
1/3495 (20130101); Y10S 318/02 (20130101); B60S
1/0848 (20130101) |
Current International
Class: |
B60S
1/32 (20060101); B60S 1/34 (20060101); B60S
001/08 () |
Field of
Search: |
;318/256,257,258,259,261,264,280,281,282,283,284,285,293,443,444,445,452,484
;15/250.001,250.12,250.17,250.2,250.31,250.32,250.33,250.34,250.35 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Ro; Bentsu
Attorney, Agent or Firm: Sales; Michael W. Denson-Low; Wanda
K.
Parent Case Text
This application is a continuation-in-part of U.S. Ser. No.
08/263,272, filed on Jun. 21, 1994, now U.S. Pat. No. 5,479,077,
issued Dec. 26, 1995.
Claims
What is claimed is:
1. A window wiper system for the window of an infrared camera
comprising:
a motor means having a shaft and responsive to an electrical drive
signal to rotate said shaft;
a wiper having one end coupled to said shaft, said wiper
having:
a wiper hub,
a wiper arm pivotally mounted to said hub, said wiper arm including
a unitarily formed member having a top surface sweeping inwardly
over half its length into an elongated front portion terminating in
a rounded nose and having respective side skirts depending from
said top surface, said side skirts each terminating in a linear
edge,
a wiper blade holder pivotally mounted to said wiper arm,
a wiper blade mounted to said holder, and
torsion spring means applying downward force on said wiper arm to
press said blade against said window; and
means for controlling the drive signal to said motor means such
that said wiper moves in an oscillatory motion across said window
between a first position and a second position, said means for
controlling further causing said motor means to stop the motion of
said wiper for a selected period of time at said second position
before causing said wiper to move toward said first position, and
for causing said motor means to stop the motion of said wiper for a
selected period of time at said first position before causing said
wiper to move toward said second position.
2. The system of claim 1 wherein said means for controlling said
drive signal includes magnetic means for sensing the position of
said shaft and generating control signals indicative thereof.
3. The system of claim 2 wherein said magnetic means comprises
first and second Hall effect sensors disposed about said shaft and
a magnetic activator fixedly mounted to said shaft.
4. The system of claim 1 wherein said means for controlling said
drive signal further decreases the magnitude of the drive signal
applied to said motor means as said wiper approaches each of said
first and second positions, thereby slowing movement of said wiper
as said first and second positions are approached.
5. The system of claim 4 wherein said means for controlling
includes:
a motor driver circuit means for generating the drive signal
applied to said motor means; and
means including a programmable logic array for supplying control
signals for controlling operation of said motor drive circuit
means.
6. The system of claim 5 further including:
delay circuit means for supplying a control signal to said
programmable logic array; and
means for supplying a control signal to said delay circuit means in
response to an output signal generated by said programmable logic
array.
7. The system of claim 1 wherein said means for controlling
includes:
a motor driver circuit means for generating the drive signal
applied to said motor means; and
means including a programmable logic array for supplying control
signals for controlling operation of said motor drive circuit
means.
8. The system of claim 7 further including:
delay circuit means for applying a control signal to said
programmable logic array; and
means for supplying a control signal to said delay circuit means in
response to an output signal generated by said programmable logic
array.
9. The system of claim 8 wherein said means for controlling said
drive signal includes magnetic means for sensing the position of
said shaft and generating control signals indicative thereof.
10. The system of claim 9 wherein said magnetic means comprises
first and second Hall effect sensors disposed about said shaft and
a magnetic activator fixedly mounted to said shaft.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The subject invention relates to window wiper systems and, more
particularly, to apparatus for controlling the motion of a
motor-driven wiper blade used in such systems.
2. Description of Related Art
Thermal vision systems capable of producing real time video
pictures in total darkness have recently been introduced for
civilian use, most particularly for law enforcement agencies. Such
systems work much like the forward-looking infrared technology used
by the U.S. military. Current Night Vision System designs depend on
clear infrared vision through an edge-heated sensor window mounted
flush with a housing.
Surface quality of such a detector window must be maintained by
keeping the surface free of rain and snow. Conventional "window
wiper" designs for windshields are large and heavy and controlled
by complex mechanical means, and are unsuitable for the compact
environment of a Night Vision infrared sensor. Designs for other
smaller surfaces, such as head lamps, are equally complex.
In copending application Ser. No. 08/263,272, a streamlined, small
scale window wiper is disclosed which is ideally suited to remove
foreign particles from an infrared detector window and thus
maintain image quality during adverse environmental conditions. The
wiper includes a wiper hub, wiper arm, wiper blade holder, and
torsion spring means. Means for controlling the window wiper
oscillating motion across the thermal imaging window is also
provided. In one embodiment, such control is achieved through the
incorporation of a suitable motor, Hall effect sensors, and an
activating magnet. In a second embodiment, such control is achieved
through the incorporation of a motor, LED sensors, and a solid disk
interrupt.
In such a system, the inventors have found that problems arise when
the motor which drives the wiper blade reverses direction.
Electrically, a voltage spike is generated, which creates
electrical wear and tear and may damage motor windings and reduce
motor life. Mechanically, a backlash is created when direction is
instantaneously reversed, which can stress and ultimately break
gear teeth.
OBJECTS AND SUMMARY OF THE INVENTION
It is thus an object of the invention to improve miniaturized
window wipers, as well as systems for actuating the same;
It is another object of the invention to provide a device for
cleaning and clearing the sensor window of a Night Vision infrared
imaging device;
It is another object to provide such a device which is compact,
lightweight, has a low part count, and is easily manufactured;
and
It is still another object to eliminate the adverse affects of
instantaneous motor reversal in motor-driven window wiper
systems.
According to the invention, control circuitry is provided which
causes the wiper blade motor to pause for a selected period of time
prior to reversing direction. The pause eliminates the adverse
electrical and mechanical effects attendant to substantially
instantaneous motor reversal.
BRIEF DESCRIPTION OF THE DRAWINGS
The just-summarized invention will now be described in connection
with the drawings of which:
FIG. 1 is a side elevational view of a miniaturized window wiper
embodiment;
FIG. 2 is a partially broken away side view of the window wiper of
FIG. 1;
FIG. 3 is a top view of the window wiper of FIG. 1;
FIG. 4 is a bottom view of the window wiper of FIG. 1;
FIG. 5 is a side sectional view of the window wiper of FIG. 1 and a
motor assembly for driving it;
FIG. 6 is a sectional view taken at 6--6 of FIG. 5;
FIG. 7 is a front view illustrating alternate apparatus for
imparting oscillatory motion to the preferred window wiper of FIG.
1; and
FIGS. 8 and 9 comprise an electrical circuit diagram of electronic
motor control circuitry according to the preferred embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following description is provided to enable any person skilled
in the art to make and use the invention and sets forth the best
modes contemplated by the inventors of carrying out their
invention. Various modifications, however, will remain readily
apparent to those skilled in the art, since the generic principles
of the present invention have been defined herein specifically to
provide a particularly useful and readily manufacturable window
wiper system and control circuitry therefor.
The preferred window wiper 11 is illustrated in FIGS. 1-5. This
window wiper 11 includes a wiper hub 16 pivotally mounted by a
first wiper pin 23 to a wiper arm 15. The wiper arm 15 is, in turn,
pivotally mounted by a second wiper pin 21 to a wiper blade holder
13. The wiper blade holder 13 mounts the wiper blade 17, for
example, in slidably inserted fashion. The respective first and
second wiper pins 21, 23 may be held in position by fasteners at
either end thereof, for example, such as rivets or so-called
"E-clips."
As shown in FIG. 2, the hub 16 includes a concealed boss 30
containing a central bore 25 for attachment to the drive shaft of a
motor, e.g., 29 (FIG. 5). The bore 25 is generally cylindrical in
cross-section with the exception of a flat face 26 which provides
for positive interlocking with a motor drive shaft.
A torsion spring 19 is located on the wiper pin 23 in order to
provide a downward force on the wiper arm 15, biasing the wiper arm
15 toward the window. A first extended arm 12 of the spring 19 is
shaped to interlock with an aperture 14 in the side of the wiper
arm 15.
The wiper arm 15 is shaped to provide a shroud over the wiper blade
holder 13 and the torsion spring 19, thereby contributing to an
aesthetic overall appearance. Thus, as seen in the top view of FIG.
3, the shroud contains a first rear portion 18 whose sides sweep
symmetrically over half its length into an elongated front portion
20 terminating in a rounded nose 22. In the side view of FIG. 1,
the wiper arm 15 exhibits a depending side skirt 24 terminating in
a linear edge 35, as well as a downward slope 27 to the nose
22.
In one exemplary embodiment, the wiper hub 16, wiper arm 15, and
wiper blade holder 13 are made of high-impact polystyrene. The
torsion spring 19 supplies a downward force on the wiper blade 17
of approximately 3.2 oz. Dimension L in FIG. 4 is approximately
N=3.939 inches.
FIGS. 5 and 6 illustrate a wiper motor assembly employing magnetic
means to control the oscillation of the wiper 11 of FIGS. 1-4. In
FIGS. 5 and 6, a motor 29 is mounted in conjunction with a
cooperating housing by means of a motor bracket 51 and O-ring seal
53. A circular retainer seal 55 is fitted over the motor shaft 41
and screwed or otherwise fastened into position on the motor
bracket 51. A switch plate 56 carrying first and second Hall effect
sensors 43 is attached to the face of the motor 29, again by
suitable screws or other fastening means. The motor bracket 51 is
then attached to the switch plate 56 by a screw or similar fastener
57. The hub 16 of the wiper 11 may be attached to the motor shaft
41 by any conventional means such as set screws, splines,
screw-type or retaining rings or clips. A retaining ring 40 is
shown in use in FIG. 5. The motor may be a reversible 12-volt DC
gear head motor.
In the embodiment of FIGS. 5 and 6, the motor 29 is controlled by
the first and second Hall effect sensors 43. A magnetic activator
or magnetic pin 45 has a magnetic element 46 (FIG. 5) attached
thereto and is positioned to rotate with the motor shaft 41 and
thereby actuate the sensors 43. The sensors 43 may be part No.
414OU as available from Allegro and connected by a suitable flex
cable 31 to cooperating switching electronics 44 which accomplish
directional switching.
Thus, in overall operation of the embodiment of FIGS. 5 and 6, Hall
effect sensor-magnetic activator interaction is used to generate
control signals for controlling oscillatory motion of the wiper 11.
The motor 29 initiates motion of both the wiper 11 and the magnetic
activator 45. The magnetic activator 45 approaches the Hall effect
sensor 43 on one side of the motor 29 and activates it. Wiper blade
direction is then reversed, which subsequently results in
activation of the second magnetic sensor. Two governor pins (not
shown) may also preferably be provided, spaced 120 degrees apart.
Such pins may serve as physical stops for the magnetic pin in order
to physically stop wiper movement should the magnetic means
fail.
The precise motion of the wiper blade 11 according to the preferred
embodiment is controlled by the motor control circuitry shown in
FIGS. 8 and 9. This circuitry is responsive to three input signals:
a "wiper discrete" signal, a forward stop switch signal FWD STOP,
and a reverse stop switch signal REV STOP. The forward stop switch
signal FWD STOP is produced by a first of the Hall effect sensors,
while the reverse stop switch signal REV STOP is produced by the
other Hall effect sensor. The wiper discrete signal signals the
circuit to begin normal oscillatory motion of the wiper 11.
The primary elements of the circuit of FIGS. 8 and 9 are a
programmable logic array (PLA) U.sub.3, a motor driver chip
U.sub.1, and a delay chip U.sub.2, the latter two components being
shown in FIG. 9. The motor driver chip U.sub.1 has output terminals
OUT A and OUT B connected directly to the terminals of the motor 29
for controlling motor operation. The PLA U.sub.3 supplies control
signals to the motor driver chip U.sub.1 to cause reversal of motor
direction, slowing of motor speed, and a time delay prior to
actuation of motor reversal. The time delay is implemented by the
delay chip U.sub.2. The PLA U.sub.3 and chips U.sub.1 and U.sub.2
in the illustrative embodiment of FIGS. 8 and 9 are conventional
off-the-shelf chips, respectively comprising PALCE16V8, UDN2953LB,
and LMC555 integrated circuits.
The circuitry of FIGS. 8 and 9 further includes three comparator
amplifiers AR1-A, AR1-B, and AR2-B, as well as a buffer amplifier
AR2-A. Each of these amplifiers may comprise LM2903 amplifier
circuits. The first comparator AR1-A is employed in setting initial
conditions of the circuit, while the second and third comparators
AR1-B and AR2-B provide noise immunity to prevent false triggers in
operation of the circuitry, as hereafter described in more detail.
Amplifier AR2-A buffers the output of the delay chip U.sub.2 into
the PLA U.sub.3.
Considering the structure and interconnection of the circuitry of
FIG. 8 in more detail, first circuitry including the first
comparator AR1-A is provided to set the initial operating
conditions of the circuit. Accordingly, the output of the
comparator amplifier AR1-A is connected over a signal line 124 to
the OUT EN input of the motor driver chip U.sub.1. The output of
the comparator AR1-A is further connected through a resistor R5 to
a +5-volt supply voltage line 111. A feedback resistor R4 is
connected between the noninverting input and the output of the
first comparator AR1-A.
The noninverting input of the comparator AR1-A is further connected
to ground through a capacitor C2 and to the junction of a voltage
divider formed by two resistors R3 and R6 connected between the
+5-volt supply and ground. The inverting input of the first
amplifier AR1-A is connected to the anode of a diode CR1 whose
cathode is connected to the +5-volt supply line 111, to one
terminal of a capacitor C1 whose second terminal is grounded, and
to one terminal of a resistor R1 connected in parallel across the
diode CR1.
The "wiper discrete" signal, which activates wiper operation, is
supplied on a first input through a series resistor R10 to the
noninverting input of the second comparator amplifier AR1-B. The
noninverting input of the second amplifier AR1-B is further
connected to ground through the parallel combination of a resistor
R11 and a capacitor C3 and to the anode of a diode CR2 whose
cathode is connected to the +5-volt supply voltage line 111. The
inverting input of the second amplifier AR1-B is connected to the
junction of a resistor R8 and a resistor R12, which pair of
resistors R8, R12 form a voltage divider between ground and the
+5-volt supply line 111.
A feedback resistor R9 is further connected between the
noninverting input and the output of the amplifier AR1-B. The
output of the amplifier AR1-B is also connected through a resistor
R7 to the +5-volt supply line 111 and to a first input I1 of the
PLA U.sub.3. The circuit including the comparator AR1-B is
implemented to provide noise immunity in the transfer of the "wiper
discrete" signal to the programmable logic array U.sub.3 such that
the potential for false triggering of the wiper operation is
eliminated.
The voltage at the inverting input to the second comparator
amplifier AR1-B is applied over signal line 115 to the inverting
input of the third noise immunity comparator amplifier AR2-B (FIG.
9). The output of the comparator AR2-B is connected to the reset
input of the delay chip U.sub.2. The noninverting input of the
comparator AR2-B is connected over signal line 117 to one terminal
of a resistor R15 whose second terminal is connected to the third
output I/O3 of the PLA U.sub.3. A diode CR4 is connected across the
resistor R15, with its anode connected to the noninverting input of
the comparator AR2-B and to a first terminal of a capacitor C8, the
second terminal of capacitor C8 being grounded. A feedback resistor
R21 has a first terminal connected over a signal line 113 to the
noninverting input 117 of the amplifier AR2-B and a second terminal
connected to the output of the amplifier AR2-B. A resistor R22
further connects the +5-volt supply line 111 to the output of the
comparator AR2-B. The circuitry including the second comparator
AR2-B is provided to again provide noise immunity such that false
triggering of the reset input of the delay chip U.sub.2 is
prevented.
The programmable logic array U.sub.3 receives the forward stop
switch signal FWD STOP and the reverse stop switch signal REV STOP
at its respective third and fourth inputs I3, I4. The VCC input of
the PLA U.sub.3 is connected to the +5-volt supply voltage by a
signal line 200 which is connected to a grounded capacitor C5. The
PLA U.sub.3 provides a motor brake control signal MOTOR BRAKE on
its first output I/O1 and over signal line 119 to the BRAKE input
of the motor driver chip U.sub.1 and a phase control signal on its
second output I/O2 and over a signal line 123 to the PHASE input of
the motor driver chip U.sub.1. The unused inputs and outputs of the
PLA U.sub.3 are grounded.
As noted above, the motor driver chip U.sub.1 provides signals for
controlling the operation of the motor 29 which is connected across
terminals E7 and E8, which are, in turn, connected to the OUT A and
OUT B outputs of the motor driver chip U.sub.1. The K input of the
motor driver chip U.sub.1 is connected through a capacitor C13 to
ground, while the RC input is connected through a resistor R25 to
ground. The VBB output of the motor driver chip U.sub.1, as well as
the ungrounded terminal of the capacitor C13 and the cathode of a
zener diode ZR1, are connected to a +12-volt auxiliary voltage,
such as an automobile battery voltage. A signal line 121 connects
the VCC terminal of the motor driver chip U.sub.1 to the +5-volt
supply. The unused terminals of the motor driver chip U.sub.1 are
grounded to a ground line 125.
The delay circuit including the delay chip U.sub.2 (FIG. 9) is used
to time the periods during which the motor is turned off prior to
reversing direction. The period may be set, for example, in the
range of 1/2 to 10 seconds. The circuitry includes a delay period
setting variable resistor R27 connected between the +5-volt supply
line 111 and the first terminal of a resistor R23, whose second
terminal is connected in common to the discharge DISCH and
threshold THRESH inputs of the delay chip U.sub.2. These inputs
DISCH and THRESH are further connected to the anode of a diode CR5
whose cathode is connected to the +5-volt supply line 111.
The second terminal of the resistor R23 is connected to a network
connected to the TRIG input of the delay chip U.sub.2. The network
includes a resistor R24 connected between the second terminal of
the resistor R23 and the TRIG input and having respective terminals
connected through respective capacitors C10, C11 to ground.
The output of the delay chip U.sub.2 is connected through a
resistor R26 to the +5-volt supply level and over a signal line 127
to one terminal of a resistor R20 whose other terminal is connected
to the inverting input of the buffer amplifier AR2-A. The output of
the buffer amplifier AR2-A is connected to the fifth input 15 of
the PLA U.sub.3, and essentially comprises a "WHICH WAY TO GO"
signal to the PLA U.sub.3, causing the PLA U.sub.3 to toggle the
motor driver chip U.sub.1 between the reverse and forward
directions of wiper drive. The buffer amplifier circuit further
includes a feedback resistor R17 connected between the noninverting
input and the output of the amplifier AR2-A. First and second
resistors R18 and R16 are connected, respectively, from the input
and the output of the amplifier AR2-A to the +5-volt supply. A
diode CR3 is further connected across the resistor R20 and has its
cathode connected to the first terminal of a capacitor C7 whose
second terminal is grounded. Finally, the noninverting input of the
amplifier AR2-A is connected to the parallel combination of a
capacitor C6 and resistor R19 whose second terminals are
grounded.
The operation of the circuitry of FIGS. 8 and 9 will now be
described in more detail. As noted, the comparator AR1-A provides a
power-up reset function. Thus, when the vehicle is turned on, the
5-volt supply is applied, and the output of the comparator AR1-A
serves to reset the wiper 11 so that it goes to the forward
position. Essentially, this defines an initial condition, a state
called "park," wherein the wiper 11 waits for a "wiper discrete"
command to begin normal operation.
More particularly, with the I1 input of the PLA at a logic "0,"
when the output of the first amplifier AR1-A goes positive (logic
"1"), a positive logic level is supplied to input terminal 12 of
the PLA and to the OUT EN input of the motor driver chip U.sub.1.
The PLA U.sub.3, in turn, provides an appropriate logic level to
the PHASE input of the enabled motor driver chip U.sub.1 which, in
turn, causes the wiper 11 to be driven toward the forward position.
When the forward stop switch E3 is activated, the PLA U.sub.3
provides the motor brake signal to the BRAKE input of the motor
driver chip, causing the motor driver chip U.sub.1 to slow or brake
the operation of the motor 29, thereby bringing the wiper blade 17
to a gradual halt at its "forward" position. The circuit is then in
the "park" state, awaiting the application of a wiper discrete
signal to the input of the second comparator amplifier AR1-B.
Application of the wiper discrete signal causes a positive logic
level (logic "1") to be applied to the I1 input of the PLA U.sub.3.
In response, the PLA U.sub.3 changes the state of the PHASE input
to the motor driver chip U.sub.1, which causes the motor driver
chip U.sub.1 to drive the wiper 11 in the reverse direction. When
the reverse stop switch is passed, and the reverse stop signal REV
STOP is produced, the PLA U.sub.3 provides the "motor brake" signal
to the motor driver chip U.sub.1, causing the wiper 11 to slow down
and come to rest in the reverse position.
The PLA U.sub.3 times the motor brake interval, and at the end
thereof, provides a signal on its output I/03 which, in turn,
causes the third amplifier AR2-B to activate the RESET input to the
delay chip U.sub.2. After the delay interval selected by the
setting of variable resistor R27 passes, the delay chip U.sub.2
provides an output to the buffer amplifier AR2-A which, in turn,
provides a positive logic level to the fifth input 15 of the PLA
U.sub.3. In response, the PLA U.sub.3 again changes the logic state
of the signal supplied to the PHASE input of the motor driver chip
U.sub.1, whereupon the motor driver chip U.sub.1 begins to drive
the wiper 11 in the forward direction towards the forward stop
switch. When the wiper 11 reaches the forward stop switch, the PLA
U.sub.3 again supplies the "motor brake" signal to slow the wiper
11 into the forward rest position and, thereafter, supplies a
signal on its third output I/03 to the third amplifier AR2-B to
again activate the delay chip U.sub.2 to time a delay interval.
After the timed delay, the PLA U.sub.3 again changes the logic
state supplied to the motor driver chip U.sub.1 to again cause the
wiper 11 to begin moving in the reverse direction.
Specific component values for the illustrative embodiment of FIGS.
8 and 9 with resistances in ohms are:
______________________________________ R1 - 1M .+-. 1% R16 - 2.49K
.+-. 1% C2 - .01 .mu.F .+-. 10% R3 - 10K .+-. 1% R17 - 10K .+-. 1%
C3 - .1 uF .+-. 10% R4 - 10K .+-. 1% R18 - 10K .+-. 1% C4 - .01
.+-. 10% R5 - 10K .+-. 1% R19 - 10K .+-. 1% C5 - .1 uF .+-. 10% R6
- 10K .+-. 1% R20 - 464K .+-. 1 % C6 - .01 .+-. 10 F R7 - 2.49K
.+-. 1% R21 - 1M .+-. 1% C7 - .1 uF .+-. 10% R8 - 10K .+-. 1% R22 -
2.49K .+-. 1% C8 - .1 uF .+-. 10% R9 - 1M .+-. 1% R23 - 10K .+-. 1%
C9 - .1 uF .+-. 10% R10 - 499K .+-. 1% R24 - 5M .+-. 5% C10 - 47 uF
.+-. 10% R11 - 499K .+-. 1% R25 - 30.1K .+-. 1% C11 - .1 uF .+-.
10% R13 - 10K .+-. 1% R26 - 10K .+-. 1% C12 - .1 uF .+-. 10 F R14 -
10K .+-. 1% R27 - 200K C13 - .1 uF .+-. 10% R15 - 499K .+-. 1% C1 -
.1 uF .+-. 10% ______________________________________
An alternate embodiment may employ optical means to supply the
forward and reverse stop switch signals FWD STOP, REV STOP, as
illustrated in FIG. 7. In particular, slotted optical switches 33
are provided on either side of the motor 29. As shown in FIG. 6,
these switches 33 may be positioned at equal angles from the
vertical, i.e., symmetrically disposed on either side of the motor
29. The switches may be LED sensor switches part No. OPB848Tx as
available from OPTEK. A solid disk interrupt 34 having a circular
slot 32 therein is fixedly attached to and moves with the motor
shaft 41.
In the embodiment of FIG. 7, the range of oscillatory motion of the
wiper 11 attached to the drive shaft 41 is controlled in response
to the interaction of the LED sensor switches 33 and the solid disk
interrupt 34. The motor 29 initiates both the motion of the wiper
11 and the solid disk 34. Throughout the permitted range of motion,
the LED sensor 33 is prevented from "seeing itself." As a result of
the solid disk interrupt, when the limit of motion is reached, a
sensor 33 does see itself, causing generation of a switching signal
and ultimate reversal of the direction of the rotation of the motor
shaft 41. This reversal is again repeated ad infinitum. In the
embodiment of FIG. 7, a governor pin 36 is provided to physically
limit the range of motion of the wiper blade 11 in the event of
failure of the optical motion limiting means.
Those skilled in the art will appreciate that various adaptations
and modifications of the just-described preferred embodiment can be
configured without departing from the scope and spirit of the
invention. Therefore, it is to be understood that, within the scope
of the appended claims, the invention may be practiced other than
as specifically described herein.
* * * * *